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  • 1.
    Jiang, Xue
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Arhammar, Cecilia
    Liu, Peng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Zhao, Jijun
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    The R3-carbon allotrope: a pathway towards glassy carbon under high pressure2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, p. 1877-Article in journal (Refereed)
    Abstract [en]

    Pressure-induced bond type switching and phase transformation in glassy carbon (GC) has been simulated by means of Density Functional Theory (DFT) calculations and the Stochastic Quenching method (SQ) in a wide range of pressures (0-79 GPa). Under pressure, the GC experiences a hardening transition from sp-and sp(2)-type to sp(3)-type bonding, in agreement with previous experimental results. Moreover, a new crystalline carbon allotrope possessing R3 symmetry (R3-carbon) is predicted using the stochastic SQ method. The results indicate that R3-carbon can be regarded as an allotrope similar to that of amorphous GC. Avery small difference in the heat of formation and the coherence of the radial and angular distribution functions of GC and the R3-carbon structure imply that small perturbations to this crystalline carbon allotrope may provide another possible amorphization pathway of carbon besides that of quenching the liquid melt or gas by ultra-fast cooling.

  • 2.
    Jiang, Xue
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Nisar, Jawad
    Pathak, Biswarup
    Zhao, Jijun
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Graphene oxide as a chemically tunable 2-D material for visible-light photocatalyst applications2013In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 299, p. 204-209Article in journal (Refereed)
    Abstract [en]

    To elucidate the usage of graphene oxide (GO) as a photocatalysis material, we have studied the effect of epoxy and hydroxyl functionalization on the electronic structure, work function, CBM/VBM position, and optical absorption spectra of GO using density functional theory calculations. By varying the coverage and relative ratio of the surface epoxy (-O-) and hydroxyl (-OH) groups, both band gap and work function of the GO materials can be tuned to meet the requirement of photocatalyst. Interestingly, the electronic structures of GO materials with 40-50% (33-67%) coverage and OH:O ratio of 2:1(1:1) are suitable for both reduction and oxidation reactions for water splitting. Among of these systems, the GO composition with 50% coverage and OH:O (1:1) ratio can be very promising materials for visible-light-driven photocatalyst. Our results not only explain the recent experimental observations about 2-D graphene oxide as promising visible-light-driven photocatalyst materials but can also be very helpful in designing the optimal composition for higher performance.

  • 3.
    Jiang, Xue
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Zhao, J.
    Li, Y. -L
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Tunable assembly of sp3 cross-linked 3D graphene monoliths: A first-principles prediction2013In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 23, no 47, p. 5846-5853Article in journal (Refereed)
    Abstract [en]

    One of the biggest challenges in graphene applications is how one can fabricate 3D architectures comprising graphene sheets in which the resulting architectures have inherited graphene's excellent intrinsic properties but have overcome its shortcomings. Two series of 3D graphene monoliths (GMs) using zigzag or armchair graphene nanoribbons as building blocks and sp3 carbon chains as junction nodes are constructued, and calculations based on first principles are performed in order to predict their mechanical and electronic properties. The perfect match between sp2 nanoribbons and sp3 linkers results in favorable energy and mechanical/dynamic stability. Owing to their tailored motifs, wine-rack-like pores, and rigid sp3 linkers, these GMs possess high surface areas, appreciable mechanical strength, and tunable band gaps. Negative linear compressibilities in a wide range are found for the zigzag GMs. By solving the problems of zero gap and dimensionality of graphene sheets simultaneously, these GMs offer a viable strategy towards many applications, e.g., microelectronic devices, energy storage, molecular sieves, sensitive pressure detectors, and telecommunication line systems.

  • 4.
    Jiang, Xue
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Zhao, Jijun
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    A novel superhard BN allotrope under cold compression of h-BN2013In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 12, p. 122204-Article in journal (Refereed)
    Abstract [en]

    Using first-principles calculations, we identify a new orthorhombic boron nitride (BN) phase (namely, P-BN; space group: Pmn2(1)), which has similar topological structure to Bct-BN and Z-BN, but without the six-membered ring. This P-BN allotrope is energetically more favorable than previously reported Pnma-BN, Bct-BN and Z-BN phases. With only 0.06 eV/atom less stable than h-BN at ambient pressure, it can be formed from h-BN under cold compression at a low pressure of 4 GPa. The theoretical hardness and bulk modulus of the P-BN crystal are 403 GPa and 60.5 GPa, respectively, comparable to those of c-BN. Moreover, the P-BN phase along with Bct-BN and Z-BN are suggested as possible intermediate phases between h-BN and w-BN, which can be qualitatively explained by two empirical rules of Ostwald and Ostwald-Volmer.

  • 5. Nisar, J.
    et al.
    Jiang, Xue
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Pathak, B.
    Zhao, J.
    Kang, T. W.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Semiconducting allotrope of graphene2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 38, p. 385704-Article in journal (Refereed)
    Abstract [en]

    From first-principles calculations, we predict a planar stable graphene allotrope composed of a periodic array of tetragonal and octagonal (4, 8) carbon rings. The stability of this sheet is predicted from the room-temperature molecular dynamics study and the electronic structure is studied using state-of-the-art calculations such as the hybrid density functional and the GW approach. Moreover, the mechanical properties of (4, 8) carbon sheet are evaluated from the Youngs modulus and intrinsic strength calculations. We find this is a stable planar semiconducting carbon sheet with a bandgap between 0.43 and 1.01eV and whose mechanical properties are as good as graphenes.

  • 6.
    Qian, Zhao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    De Sarkar, Abir
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Maark, Tuhina Adit
    Jiang, Xue
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Deshpande, Mrinalini D.
    Bououdina, Mohamed
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Pure and Li-doped NiTiH: Potential anode materials for Li-ion rechargeable batteries2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 3, p. 033902-Article in journal (Refereed)
    Abstract [en]

    Pure and Li-doped NiTiH hydrides have been explored for their potential applications as anode materials for Li-ion batteries using density functional theory. The diffusion of Li-ion through pure NiTiH lattice has revealed a big enhancement at 600 K with the diffusion coefficient estimated to be 2.3 x 10(-10) m(2) s(-1) or so. The most thermodynamically stable Li-doped NiTiH material has been ascertained, which evidently shows enhanced electrochemical capacity and a minor increase in voltage and unit-cell volume with respect to pure NiTiH.

  • 7.
    Qian, Zhao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Jiang, Xue
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    De Sarkar, Abir
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Adit Maark, Tuhina
    Deshpande, Mrinalini
    Bououdina, Mohamed
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Screening study of light-metal and transition-metal-doped NiTiH hydrides as Li-ion battery anode materials2014In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 258, p. 88-91Article in journal (Refereed)
    Abstract [en]

    Here we have investigated systematically the effects of various light-metals (Mg, Al) and transition-metals (V, Cr, Mn, Fe, Co, Cu, Zn) on the electrochemical properties of NiTiH hydrides as anodes for Li-ion battery applications. Based on the pristine NiTiH, a screening study in terms of the structure volume, average voltage and specific capacity has been performed to choose the most proper metal dopants. The most thermodynamically stable doping sites (Ni or Ti site) of various dopant metals have been determined respectively. It is finally summarized that in this study, the light metal Al or the transition metals Cr, Mn and Fe have the most comprehensive effects and are the most promising metal dopants for the pristine NiTiH hydride. This theoretical study is proposed to help understand the properties of the material and guide the design and development of more efficient metal-hydrides materials for Li-ion battery anode applications.

  • 8.
    Wang, Baochang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Århammar, Cecilia
    Jiang, Xue
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Arauji, Carlos Moyses
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    A Comparison Between Hybrid Functional, GW Approach and the Bethe Salpether Equation: Optical Properties of High Pressure Phases of TiO22014In: Science of Advanced Materials, ISSN 1947-2935, E-ISSN 1947-2943, Vol. 6, no 6, p. 1170-1178Article in journal (Refereed)
    Abstract [en]

    Titanium dioxide has good corrosion resistance in aqueous solutions and is a good candidate for photoelectrodes. The limitation of the anatase phase of TiO2 is its large band gap. High pressure phases of TiO2 like fluorite, pyrite and cotunnite may possess a more suitable band gap than the well known atmospheric phases. In this paper, the electronic properties of high pressure phases of TuO(2), fluorite, pyrite and cotunnite, have been investigated by hybrid functional and GW methods. Our calculations suggest that the band gap of fluorite and pyrite phases have optimal band gaps to absorb visible light for photocatalysis to decompose water. The imaginary part of the dielectric function has also been calculated for fluorite, pyrite, cotunnite and anatase phases using the Bethe-Salpether (BSE) method. The dielectric function calculated by BSE for the anatase phase agrees well with experiment and with previous studies, using the same level of theory. Therefore we expect that we are also able to predict the optical properties of the high pressure phases of TiO2 by the BSE method. The spatial properties and the localization character of excitons in these high pressure phases were investigated and discussed in terms of photoconversion efficiency.

1 - 8 of 8
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